Bioremediation of Methyl Parathion by Bacterial Strains Isolated from Fresh Vegetables

Methyl parathion, an organophosphate and cholinesterase inhibitor, is a widely used pesticide. In the present study, fresh vegetables were sampled to enumerate parathion resistant microbes. Nitrite, sulphite and hydrazine levels along with microbial load of the vegetables were determined. Bean, red spinach and coriander contained higher percentages of gram positive bacteria whereas beet ischolar_main and cabbage showed prevalence of gram negative species. Sixty bacterial strains were found to show resistance against 2000/m1 parathion and 5% of these had MIC values above 10000/m1. A gram negative bacterial strain BG023, isolated from bitter gourd surface showed maximal hydrolysis of parathion (MIC 12000/m1). In the absence of other carbon sources, the organism exhibited a faster degradation of parathion with simultaneous utilization of major detectable product p-nitrophenol during the late stationary phase of growth. The gene for parathion hydrolase was found to be plasmid borne since curing with 15 mg/ml SDS resulted in cells which failed to grow in presence of parathion but showed normal growth otherwise. The organism was also resistant to widely used antibiotics like ampicillin, vancomycin, amoxyclav, norfloxacin, bacitracin, etc. After pathogenicity testing, the organism can be used to reduce the load of organophosphate pesticides in agricultural fields.